Phonograph pickup unit



Patented Oct. 18, 1949 PHONUGRAPH PICKUP UNIT Stanley R. Emm -Cambridge, Mass., assignorto Tobe.Deutschmann,-=.Ganton,;Mass.

Application March 8, 1946, Serial'No. 652,926

.18 Claims. 1

The 'present invention relates to a phonograph pick-up unit for converting mechanicaliv'ibrations into corresponding electrical vibrations or *vice -versa, and is 'particularlyuseful lathe-reproductionof soundirom phonograph records, but may -of course-be applicable to any other type of energy conversion between mechanical vibrations and correspondingelectrical current.

'The present-invention'is an improvement-over my copending patent application Serial No. 624,362, 'filed'October 25, 1945, now 1U. S. Patent No. 2-,471,542, granted May '31, 1949, and'relates "to various other-means Y for the conversionbetween mechanical vibrations andelectricalcurrentthan shown inthe above application.

Incommon with the means of the application referred to above, the structures oi the present invention use a magnetostrictive wire or rod under tension or =torsion 'or under the combination of both such'strains in the means forinterchanging mechanical and r electric energy.

The present invention will be more ifully described and :explained in :connection with th'e embodiment of the same as illustrated :by the drawings, in which:

Figure l. showsa sectional viewof'one form-of the invention.

Figure 2 shows a section taken on :theline 2-2 of Figure .1.

Figure .3 shows'a:fragmentarysection taken on the-line 3--3 of Figurel.

Figure 4 shows a modification of the dorm showntin Figure 1 withelemerrts in fragmentary section.

'Figurefi shows an enlarged \view eof a detail=of Figure '4 as viewediromitherigl'itof Figure i.

Figure '6 shows a still further modified iform in-a sectional view, and

Figure 7 shows an enlarged detail 'of the form of Figure 6.

In the modification shown in Figures 1 to 3, the pick-up unit comprises a frame :formed "day two end plates, [and 2 of magnetizable material, such "for instance as iron'having'a low=reluctance for-the flow of magnetic rfiux. Betweentheseend plates I and 2 there may :be positioned one 'or more bars,-3'-3 etc., of permanentmagnetmaterial, such as an alloy of nickel and'copp'er known by the trade name as 'Alnico, -or some other similar material which hasa high magnetizing force.

The plates 1 and 2 may be :bolted together by long bolts 4, 4, etc., 'of non-.magnetic :material. Spaced between the two end plates I and"! may be --'also .a coil '5 serving *to act as a transmitter 5 or as a receiver, depending upon whether the stylusdi 'is to be used for cutting purposes-or to rrun'over therecord and pick up the vibrations dueto the soundtrack in the record. Thecoil 5 may be wound one .form I and be clamped in placeby means of an end plate 8 abutting-against the plate or bar 2. The coil '5 surrounds the magnetostrictive wire 9. One end of the wire 9 may be fixed inan end plate HI, which rests on the'screw cap l3. The screw-cap I3 is threaded into a collar M which is clamped-to the front end of the bar or plate 2 through outwardly extending flanges I5 through which the screws 16 pass to clamp the collar in place. The cap l3 may be turned to' backaway from-the end plate 10 to provide desired tension on the wire 9. The lower end of the magnetostrictive wire is bent at ran angle :over the outer face of the lower base "plate -l, which may be covered with a layer of clamping material to clamp the arm portion of the wire to which the stylus G is attached. Tension on "the wire "9 is exerted between the plate l0 and the angle portion at the other end lying 'over the plate.

The permanent magnet formed by-the bars3, 3, maybe assumed to make the gapin the bar I a southpdle and the gapin the bar 2 anorth pole, in which case when the-coil '5 is energized in one :direction, the flux will be increased tending to contract Zthe magnetostrictive wire, if made of nickel; and in the other case when the current is reduced in the coil 5 or flows in the opposite "direction, the flux in the wire will decrease and the'wire'willbe permitted to expand. This vibrationwill betransmitted tothe stylus 6 and cause it to vibrate in accordance with the sound and electrical undulations impressed upon-the circuit. --'1\s'a*receiver the stylus 6 will be vibrated and *causethemagnetostrictive wireto perform similar vibrations which will induce corresponding "currents in the coil '5 which may be amplified and reproduced.

The magnetostrictive wire 9 passes through a hole 19 at thetop pole and through a similar hole zflatthe lower pole. The permanent magnethas =an effect of producing a definite polarization on the wire '9, while the signal or voice current impressed-upon the coil 5 will produce the change ln'fiux in the wire 9 which will cause its vibration, or if'the stylus causes the wire to move, the flux will be varied inducing corresponding currentsfiin coil 5.

In the arrangement shown in' Figures 4 and 5, the magnetic z'circu'it is shown somewhat difierently than :that shown inFigures 1 and 2. Here the permanent magnet 2| is formed as a U- shaped element and a magnetostrictive wire 22 passes through the open end of the U-shaped magnet either through holes 23 or 24 formed in the ends of the magnet or through grooves which may be covered to support the wire therein, if necessary. The magnetostrictive wire at the end 23 is provided with an angular extending arm 25 which sets in a groove or slot in the outer face of the pole. A coil 26 is supported between the two poles 23 and 24 and surrounds the magnetostrictive wire 22. This coil 25 may be supported by a bracket support or in any other suitable manner as indicated at 21. The magnetostrictive wire has attached to it the stylus 28 either at its mid-point or somewhere between the ends. The magnetostrictive wire is supported at its other end in a hole 29 in the adjustable angular arm or bracket 39. The magnetostrictive wire passes through the hole 29 and may be given atorsional strain by setting the turned-in arm 3! with its projection 32 in any one of the holes or recesses 33 (Fig. 5), thereby producing the desired torsional strain on the wire. The arm 3% is adjustable longitudinally with respect to the magnetostrictive wire and thereby the wire 2?. may be put in tension by means of turning the adjusting screw 34. By turning this screw 34 the arm may be moved outward giving additional strain to the wire 22. When the desired strain has been obtained, the arm 39 is clamped in position by means of the clamping screw 35 which passes through a slot in the arm and clamps the arm to the base of the magnet 2!. The supporting arm 30 is preferably not of magnetic material.

In the arrangement shown in Figures l and 5, both torsion and tension may be imparted to the magnetostrictive wire 22, to the exact desired degree.

A further modification of the invention is shown in Figures 6 and '7. In this case the magnetostrictive wire 36 may be surrounded with two cylindrical coils 31 and 38 contained within cylinders 39 and 40, respectively, which are permanent magnets and may be magnetized with the external end of the magnet 39 as a south pole and the internal end as a north pole, while the magnet 40 has its internal end as a south pole and has its external end as a north pole. The magnetostrictive wire is supported at the left end by means of a plate 41 which is fixed in an end cap 4-2 extending over the end of the cylinder 39. This cap is provided with recesses 43 spaced around its edge as indicated in Figure 7, and the cylinder 39 is provided with a pin 44 so that the cap may be turned in any position to give the wire 36 the desired torsion. The other end of the magnetostrictive wire is fixed in a cap 45 permanently and the outside of the cylinder 40 is threaded as indicated at 43 with a tension adjusting nut 41 engaging the threaded section of the cylinder. The threaded nut or collar 41 may be turned to extend the cap 45 in a direction longitudinal with the wire 36 and exert a tension on it. The cylinders 39 and 40 at their inner ends fit into a base 48 which has shoulder portions forming collars or sleeves within which the cylinders 39 and 4!! rest. The base 48 is provided with a hole at the center through which the wire 36 passes and also a passage extending radially as indicated at 49, through which the stylus 50 extends. The stylus 50 works under torsion to produce vibrations in a plane perpendicular to the paper as shown in Figure 6. An increase in flux through the magnetostrictive wire 36 will increase the tension and therefore rotate the stylus in the direction of increased torsion. A decrease in flux will have the opposite effect. As a reproducer of sound the same principles will, of course apply.

Having now described my invention, I claim:

1. A phonograph pick-up device comprising a magnetostrictive wire, means supporting said wire at both ends, a stylus extending in a direction away from the wire with one end firmly attached thereto and the other end free, means for magnetizing said wire only on one side of the position of the stylus, and coil means contained within the magnetizing means for impressing on the wire or receiving therefrom, electrical oscillations corresponding to the mechanical vibrations thereof.

2. A phonograph pick-up device comprising a magnetostrictive Wire, means supporting said wire at both ends, a stylus extending in a direction away from the wire with one end firmly attached thereto and the other end free, means for magnetizing said wire only on one side of the position of the stylus, and coil means contained within the magnetizing means for impressing on the wire or receiving therefrom, electrical oscillations corresponding to the mechanical vibrations thereof, and means applied only at the sup porting ends comprising in part said supporting means for providing a biasing torsional strain on said wire between the points of support.

3. A phonograph pick-up device comprising a magnetostrictive wire, means supporting said wire at both ends, a stylus extending in a direction away from the wire with one end firmly attached thereto and the other end free, means for magnetizing said wire only on one side of the position of the stylus, and coil means contained within the magnetizing means for impressing on the wire or receiving therefrom, electrical oscillations corresponding to the mechanical vibrations thereof, and means applied only at the supporting ends comprising in part said supporting means for providing a biasing torsional and tensional strain on said wire between the points of support.

4. A phonograph pick-up device comprising a magnetostrictive wire, means supporting said wire at both ends, a stylus extending in a direction away from the wire with one end firmly attached thereto and the other end free, means for magnetizing said wire only on one side of the position of the stylus, comprising a U-shaped permanent magnet having pole ends adjacent the wire, a coil surrounding said wire between said pole ends for impressing oscillations thereon and receiving oscillations from the wire, and means applied only at the supporting ends for exerting a biasing tension between the ends of the wire.

5. A phonograph pick-up device comprising a magnetostrictive wire, means supporting said wire at both ends, a stylus extending in a direction away from the wire with one end firmly attached thereto and the other end free, means for magnetizing said wire only on one side of the position of the stylus, and coil means contained within the magnetizing means for impressing on the wire or receiving therefrom electrical oscillations corresponding to the mechanical vibrations thereof, and means applied only at the supporting ends comprising in part said supporting means for providing a biasing tensional strain in said magnetostrictive wire.

6. A phonograph pick-up device comprising a magnetostrictive wire, means supporting said wire at both ends, a stylus extending in a direction away from the wire with one end firmly attached thereto and the other end free, means for ma netizing said wire only on one side of the position of the stylus, comprising a U-shaped permanent magnet having pole ends adjacent the wire, a coil surrounding said wire between said pole ends for impressing oscillations thereon and receiving oscillations from the wire, and means applied only at the supporting ends for exerting a torsional strain between the ends of the wire.

7. A phonograph pick-up device comprising a magnetostrictive wire, means supporting said wire 'at one end, means impressing a permanent magnetic field on said wire between its ends, coil means surrounding said wire within the positions of the poles of the permanent magnet, and means for supporting the other end of the magnetostrictive wire in adjustable tension and torsion, comprising a bracket, adjustable in the longitudinal direction of said wire with respect to said first supporting means for supporting the other end of said Wire in the desired tension and means for applying and maintaining the end of said wire in permanent torsional position.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 351,905 Eickemeyer Nov. 2, 1886 1,882,400 Pierce Oct. 11, 1932 2,348,852 Mallina May 9, 1944 

